One particularly useful approach for investigating protein folding is ‘The Fold Approach’, which involves a detailed analysis of the folding of several topologically, structurally and/or evolutionarily related proteins in order to discern patterns and trends in folding (stability, pathways and mechanisms). We are now applying this approach to the folding of intrinsically disordered proteins.The three systems we are studying all involve formation of helical structure when a disordered protein binds its target. The properties of these systems are vastly different, from µM - nM binding affinity and with association and disassociation rate constants varying by many orders of magnitude. This brings different challenges for determining the kinetics of assembly and disassembly.We can use protein engineering approaches, pioneered in protein folding studies to investigate the mechanism of binding, ask whether the presence of residual structure in the disordered peptide affects binding, and investigate the importance of solvent.Our results challenge some of the long held views on IDPs - how important residual structure is to binding; the idea that IDPs are special in conferring high specificity combined with low affinity. Can we relate biophysical properties to specific IDP functions?